Manufacture of artificial filaments, threads, yarns, and the like



Patented Nov. 7, 1939 UNITED STATES PATENT OFFICE MANUFACTURE OF ARTIFICIAL FILAIVIENTS, THREADS, YARNS, AND THE LIKE No Drawing. Application July 21, 1933, Serial No. 681,492. In Great Britain August 6, 1932 8 Claims.

This invention relates to improvements in the manufacture of artificial products and more particularly to the manufacture of filaments, yarns, threads and the like from solutions of cellulose acetate or other cellulose esters or ethers. This application is a continuation-in-part of application S. No. 523,929 filed March 19, 1931.

In U. S. Patents Nos. 1,465,994 and 1,467,493 and U. S. applications S. Nos. 402,785 filed October 20, 1929, 418,414 filed January 3, 1930, 437,423 filed March 20, 1930, 469,622 filed July 21, 1930, 593,859 filed February 18, 1932, 601,043 filed March 24, 1932, and 607,668 filed April 26, 1932, there is described inter alia the manufacture of filaments, threads, yarns and the like from solutions of cellulose acetate or other cellulose esters or ethers by extruding such solutions into coagulating baths containing solvents or other softening agents for the cellulose derivatives. In'particular the coagulating baths may be aqueous in character. U. S. Patent No. 1,465,994 describes such processes broadly; specifying relatively low concentrations of the solvent or other softening agent, while the later specifications are addressed particularly to the use of a coagulating bath 'in which the solvent concentration is high or in which the filaments continuously with coagulation are subjected to the action of a solvent or other softening agent in high concentration. The

. concentration may for instance be sufficiently high to cause coalescence of the individual filaments if they are brought together, the volume of bath carried with the filaments preventing such coalescence during the actual coagulation of the materials.

The present invention also relates to such processes wherein coagulation of the filaments, threads or the like is efiected in' a medium containing a solvent for the cellulose derivative. We have now found that it is of great advantage to carry out processes such as those described above with the same solvent in the coagulating bath as that present in the spinning solution. A mixture of solvents or solvent mixture may be employed, but in accordance with the present invention the same mixture must also be present in the spin{ ning solution. We have found, moreover, that it is particularly advantageous to employ solvents having boiling points higher than, or at least not lower than, the non-solvent present in the coagulating bath, or which are at least not substantially more volatile than the non-solventmedium under the conditions obtaining.

By this means great economy is effected in the recovery of the solvent from the coagulating bath,

since there may be only one solvent present, or if there are two or more solvents, all are used to reconstitute the spinning solution and the coagulating bath, and in addition there appears to be a more ready permeation of the filaments, threads and the like by the coagulating bath than is the case when the solvent employed in the bath is different from that present in the spinning solution. Preferably in accordance with the present invention a single solvent is used in the coagulating bath, and this solvent is the sole solvent present in the spinning solution. The solvent to be used in accordance with the present invention is preferably substantially neutral, since solvents such as acetic acid are difficult to remove from the filaments and are somewhat objectionable if retained therein, while formic acid definitely has a deleterious effect. Thus the solvent may be glycol mono-acetate, methyl glycol mono-acetate, or other esters 'or ether-esters of olefine or polyolefine glycols, diacetone alcohol, ethyl lactate, diethyl tartrate, dioxane, methylene ethylene dioxide and other cyclic ethers and also the homologues and substitution products thereof, for instance the esters, ethers and ether-esters of dioxane dicarbinol. All the above solvents are soluble in water, and we prefer to carry out the coagulation in an aqueous bath containing the said solvents. However, the invention is not limited to aqueous baths, and other non-solvents, e. g. alcohol or even hydrocarbons, may be used as the non-solvent present in the bath. Preferably, however, water miscible solvents and nonsolvents are employed.

The solvent is preferably so chosen that by reason of its innocuous properties it need not be washed out or entirely washed out of the filamentsor other products, and a residue of solvent may remain therein or may be removed by evaporation only. When evaporation is relied upon or takes place, it is desirable in order to obtain lustrous filaments and similar products to employ a solvent which is less volatile under the spinning conditions than is the non-solvent used in the coagulating bath. For this reason we prefer to use diacetone alcohol, ethyl lactate, glycol mono-acetate and methyl glycol mono-acetate among the solvents specified above.

As previously indicated the spinning solutions are made up by dissolving the cellulose acetate or other cellulose ester or ether in the solvent to be used in the coagulating bath. In some cases the solvents mentioned above are not of such high solvent power as is acetone, the usual solvent used for making up cellulose acetate As described in U. S. application S. No. 469,622

the bath may contain salts, sugars or like subtances which are adapted to decrease the solubility of the solvent present in the coagulating bath in the non-solvent present therein. Such substances are preferably non-volatile and not decomposable under conditions which serve to recover the solvent from the bath, and particularly at the temperature required for distillingv off the solvent or the non-solvent where distillation takes place. Treatment with salts, sugars and the like may also be applied subsequent to coagulation, as described in U. S. application S. No. 638,179 filed October 17, 1932.

The solvent may be present in the coagulating bath in any convenient concentration. By reason of the fact that the same solvent is present in the spinning solution comparatively low concentrations of solvent may be present in the coagulating bath, for example concentrations of the order of 5 to 10 to 15%. However, higher concentrations, such as -40%, may be used provided that at the speed of spinning an' effective coagulation takes place in the bath so that the products are sufficiently hardened to admit of their being handled after emergence from the bath.

During or continuously with coagulation a stretch may be imparted to the filaments or threads so that fine filament deniers may be produced from relatively large jet orifices. Such stretch may act on the materials immediately on their emergence from the spinning orifices, or means may be employed whereby the stretching tension is wholly or partially prevented from extendingback to the jet. Thus the materials may contact with rollers, fork tension devices or the like situated between the draw roller and the jet, or the coagulating bath may be caused to move in a direction counter to that of the travel of the materials. In this connection reference is made broadly to U. S. applications S.

' or in two or more stages, e. g. as described in U. S.

application S. No. 573,424 filed November 6, 1931.

By suitably adjusting the proportions of solvent present during the coagulation, filaments, threads, ribbons or other products of almost any desired degree of lustre may be produced, for example products having practically no lustre, products having a lustre similar to that of natural silk or products having a relatively high lustre. In general the higher the concentration of the solvent present during coagulation the higher will be the lustre of the products.

In any of the processes of the present invention non-solvent media may be added to the solution of cellulose derivatives before spinning or extrusion, the quantity of non-solvent media being varied from nil to an amount which just fails to precipitate the cellulose derivative. The non-solvent used may be, and preferably is, the same non-solvent as that present in the coagulating bath so as still further to facilitate working up of the baths. Furthermore the coagulating bath may, if desired, include a lubricant, for instance an oil, so as to lubricate the threads. or filaments for subsequent textile operations. The lubricant may, for example, be present in the form of an emulsion or as an oil or other layer on the bath. I

After emergence from the bath and before collecting the products, for instance on bobbins, in the form of cheeses, etc., excess of solvent may be washed out or otherwise removed from the products. The excess solvent may be removed, for example, by washing with water or other nonsolvent media, with salt solutions or with solutions of solvents of lower concentration than those adhering to the products. Washing may, if desired be effected with solutions of salts or solvents of continually or continuously decreasing concentration. The washing may be effected, for example, by spraying or in a centrifugal spinning box, or by passing the materials through baths containing the washing agent. If desired, a portion of the coagulating bath may be employed for washing the materials, as is described in U. S. application S. No. 668,071 filed April 26, 1933.

Excess solvent may also be removed by evaporation, the process being applied either directly to the materials emerging from the coagulating bath, or after a washing step. The lustre of the products may be varied by a suitable choice of solvent andnon-solvent; thus the use of a solvent which is removed less quickly than the nonsolvent, so that the solvent power of the liquid medium in contact with the materials does not tend to decrease, favours the production of materials of high lustre. When such products are required, therefore, the use of a solvent having a vapour pressure lower than that of the nonsolvent is desirable, if the liquid medium is to be removed by an evaporative process.

The invention is applicable broadly to the manufacture of filaments, threads, ribbons and the like of acetone soluble cellulose acetate, which is by far the most important of the cellulose derivatives, or any other cellulose acetate or any other cellulose ester, ether or ether-ester, for example cellulose formate, cellulose propionate, cellulose butyrate or mixed esters, for example cellulose nitro-acetate, methyl, ethyl or benzyl cellulose or mixed ethers, ethyl cellulose acetate or oxy-ethyl cellulose acetate.

The following examples are given in order to illustrate the invention but they do not of course limit it in any way:

Example 1 A 20% solution of cellulose acetate in dioxane is spun through suitable orifices into a 50% aqueous solution of dioxane at 25 C. and the bundle of filaments obtained-then passes under a guide and round a draw-roller rotating at a peripheral speed of 70 metres per minute. From the draw-roller the materials pass to suitable washing and drying devices and are then wound or twisted and wound, e. g. in a centrifugal spinning box.

Example 2 An 18% solution of cellulose acetate in methyl glycol mono-acetate is spun, into a 37% aqueous solution of methyl glycol mono-acetate at 25 C. The bundle of filaments obtained is passed round a draw-roller rotating at a peripheral speed of 50 metres per minute, and then to washing, drying and winding devices.

Example 3 A 15% solution of cellulose acetate in glycol mono-acetate is spun into a 45% aqueous solution of glycol mono-acetate at C. and the bundle of filaments obtained is passed round a draw-roller rotating at a peripheral speed of 40 metres per minute, and then proceeds to washing, drying and winding devices.

In all the preceding examples the peripheral speed or" the draw-roller may be greater than the rate of extrusion, so that the products are drawn down to fine deniers. It is to be understood that the term solvent medium employed in the following claims includes a medium comprising a true solvent or a mixture of true solvents, or a solvent mixture. The term solvent mixture is employed in this application to denote a mixture of liquids which individually are not solvents for the cellulose derivative, but which together form a solvent medium.

What we claim and desire to secure by Letters Patent is:

1. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of an organic derivative of cellulose in a solvent medium through a shaping device into a coagulating liquid containing a high concentration of the same solvent medium together wtih a non-solvent for the organic derivative of cellulose, and subjecting the coagulated products to a drying operation, the solvent medium comprising a constituent which is less volatile at the drying temperature than is the said non-solvent.

2. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of cellulose acetate in a neutral solvent medium through a shaping device into an aqueous coagulating liquid containing the same solvent medium, and subjecting the coagulated products to a drying operation while they still contain solvent medium, the solvent medium comprising a true solvent which is less volatile at the drying temperature than water.

3. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of an organic derivative of cellulose in a neutral solvent medium through a shaping device into a coagulating liquid containing the same solvent medium together with a non-solvent for the organic derivative of cellulose, and subjecting the coagulated products to a drying operation while they still contain solvent medium, the solvent medium comprising a true solvent which is less volatile than the said non-solvent under the drying conditions obtaining, so that during the drying operation the ratio of the concentration of non-solvent to the concentration of solvent in the coagulating liquid on the products does not increase.

4. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of an organic derivative of cellulosein a neutral solvent medium through a shaping device into a coaguretain some solvent for the cellulose derivative after all the non-solvent has been removed.

5. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of cellulose acetate in methyl glycol mono-acetate through a shaping device into an aqueous solution of methyl glycol mono-acetate, and thereafter drying the products while they still contain methyl glycol mono-acetate.

6. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of cellulose acetate in glycol mono-acetate through a shaping device into an aqueous solution of glycol mono-acetate, stretching the products continuously with their production, and thereafter drying the products while they still contain glycol mono-acetate.

7. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of an organic derivative of cellulose in a neutral solvent medium through a shaping device into a coagulating liquid containing the same solvent medium together with a non-solvent for the organic derivative of cellulose, subjecting the products continuously with their production to a stretching operation, and drying the products while they still contain solvent medium, the solvent medium comprising a true solvent which is less volatile than the said non-solvent at the drying temperature.

8. Process for the manufacture of artificial filaments, threads, yarns, ribbons and like products, which comprises extruding a solution of cellulose acetate in a neutral solvent medium through a shaping device into a coagulating liquid containing a high concentration of the same solvent medium together with a non-solvent for the cellulose acetate, subjecting the products continuously with their production to a stretching operation, the stretching tension being wholly or partially prevented from acting on the product immediately upon its extrusion from the shaping device, and drying the products while they still contain solvent medium, the solvent medium com-- 

